Java NoClassDefFoundError，但存在类

如果启动以下代码，我会得到以下Android异常。我有一个服务器-客户机应用程序和一个相互通信的服务器代理。现在我只是在Android应用程序中得到了这个异常，而不是在服务器代理上。我知道这在一段时间以前是有效的

12-18 20:36:41.626: E/AndroidRuntime(19441): FATAL EXCEPTION: AsyncTask #1
12-18 20:36:41.626: E/AndroidRuntime(19441): java.lang.RuntimeException: An error occured while executing doInBackground()
12-18 20:36:41.626: E/AndroidRuntime(19441):    at android.os.AsyncTask$3.done(AsyncTask.java:299)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at java.util.concurrent.FutureTask.run(FutureTask.java:239)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at java.lang.Thread.run(Thread.java:841)
12-18 20:36:41.626: E/AndroidRuntime(19441): Caused by: java.lang.NoClassDefFoundError: de.hska.ilias.commons.server.Communication
12-18 20:36:41.626: E/AndroidRuntime(19441):    at de.hska.ilias.app.client.Client.handleServerPassword(Client.java:101)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at de.hska.ilias.app.client.Client.manageHandshake(Client.java:75)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at de.hska.ilias.app.client.LoginTask.doInBackground(LoginTask.java:85)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at de.hska.ilias.app.client.LoginTask.doInBackground(LoginTask.java:1)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at android.os.AsyncTask$2.call(AsyncTask.java:287)
12-18 20:36:41.626: E/AndroidRuntime(19441):    at java.util.concurrent.FutureTask.run(FutureTask.java:234)
12-18 20:36:41.626: E/AndroidRuntime(19441):    ... 4 more
12-18 20:36:41.956: E/WindowManager(19441): Activity de.hska.ilias.app.activity.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{43168430 V.E..... R......D 0,0-1026,288} that was originally added here
12-18 20:36:41.956: E/WindowManager(19441): android.view.WindowLeaked: Activity de.hska.ilias.app.activity.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{43168430 V.E..... R......D 0,0-1026,288} that was originally added here
12-18 20:36:41.956: E/WindowManager(19441):     at android.view.ViewRootImpl.<init>(ViewRootImpl.java:450)
12-18 20:36:41.956: E/WindowManager(19441):     at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:258)
12-18 20:36:41.956: E/WindowManager(19441):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:73)
12-18 20:36:41.956: E/WindowManager(19441):     at android.app.Dialog.show(Dialog.java:287)
12-18 20:36:41.956: E/WindowManager(19441):     at de.hska.ilias.app.client.LoginTask.onPreExecute(LoginTask.java:73)
12-18 20:36:41.956: E/WindowManager(19441):     at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
12-18 20:36:41.956: E/WindowManager(19441):     at android.os.AsyncTask.execute(AsyncTask.java:534)
12-18 20:36:41.956: E/WindowManager(19441):     at de.hska.ilias.app.client.Client.tryConnect(Client.java:44)
12-18 20:36:41.956: E/WindowManager(19441):     at de.hska.ilias.app.ui.action.LoginAction.onClick(LoginAction.java:77)
12-18 20:36:41.956: E/WindowManager(19441):     at android.view.View.performClick(View.java:4475)
12-18 20:36:41.956: E/WindowManager(19441):     at android.view.View$PerformClick.run(View.java:18786)
12-18 20:36:41.956: E/WindowManager(19441):     at android.os.Handler.handleCallback(Handler.java:730)
12-18 20:36:41.956: E/WindowManager(19441):     at android.os.Handler.dispatchMessage(Handler.java:92)
12-18 20:36:41.956: E/WindowManager(19441):     at android.os.Looper.loop(Looper.java:137)
12-18 20:36:41.956: E/WindowManager(19441):     at android.app.ActivityThread.main(ActivityThread.java:5419)
12-18 20:36:41.956: E/WindowManager(19441):     at java.lang.reflect.Method.invokeNative(Native Method)
12-18 20:36:41.956: E/WindowManager(19441):     at java.lang.reflect.Method.invoke(Method.java:525)
12-18 20:36:41.956: E/WindowManager(19441):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
12-18 20:36:41.956: E/WindowManager(19441):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
12-18 20:36:41.956: E/WindowManager(19441):     at dalvik.system.NativeStart.main(Native Method)

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NoClassDefFoundError指定该类在运行时不可用。确保它位于类路径中，或者静态初始值设定项if present没有中断。对于后面的示例，您将在stacktrace下面的某个地方看到ExceptionInInitializerError。我建议您仔细研究一下，我已经找到了解决这个问题的方法：Java编译器符合性级别，在Android项目中设置为1.6，在依赖Java项目中设置为1.7。将两者都设置为1.6后，解决了问题，但我不知道为什么

你确定班上有人吗？此外，静态初始值设定项中引发的异常也可能导致NoClassDefFoundErrors。de.hska.ilias.commons.server.Communication是否有初始化为值的静态初始值设定项/静态变量？Communication类有静态方法，但没有初始值设定项。我对Android问题一点也不了解，但您可能知道，这是一个运行时错误。这意味着它与运行时找不到的类有关，也就是说，您的构建路径没有问题。此链接可能会让您了解：

  private void handleServerPassword() throws ServerPasswordException
  {
    try
    {
      **if (Communication.rcvLineServerPasswordReq(input))**
      {
        Communication.sndServerPasswordAck(output);
        Communication.sndServerPassword(output);
      }
      else
        throw new ServerPasswordException();
    }
    catch (ServerPasswordException e)
    {
      throw new ServerPasswordException("Handling password communication failed.");
    }
  }